Method, apparatus, and medium for video processing

Abstract

Embodiments of the present disclosure provide a solution for video processing. A method for video processing is proposed. In the method, for a conversion between a current video block of a video and a bitstream of the video, at least one cross component prediction (CCP) model for the current video block is determined based on at least one history table (HT) of CCP models. The conversion is performed based on the at least one CCP model. The at least one history table of CCP models is updated before or after coding a video unit.

I/We claim: 
     
         1 . A method for video processing, comprising:
 determining, for a conversion between a current video block of a video and a bitstream of the video, at least one cross component prediction (CCP) model for the current video block based on at least one history table (HT) of CCP models; and   performing the conversion based on the at least one CCP model,   wherein the at least one history table of CCP models is updated before or after coding a video unit.   
     
     
         2 . The method of  claim 1 , wherein the at least one CCP model comprises at least one of:
 a cross-component linear model (CCLM),   a variant of CCLM,   a convolutional cross-component model (CCCM), or   a variant of CCCM.   
     
     
         3 . The method of  claim 1 , wherein the at least one history table is updated at a beginning of coding the video unit comprising the current video block, the video unit comprising at least one of: a sequence, a picture, a slice, a tile, a sub-picture, a coding tree unit (CTU), or a CTU row, and/or
 wherein updating the at least one history table comprises one of: emptying the at least one history table; or filling the at least one history table with default entries.   
     
     
         4 . The method of  claim 1 , wherein the at least one history table is updated after coding the video unit, the video unit comprising a coding unit (CU), and/or
 wherein a dual-tree coding is applied, and the coding unit comprises a chroma coding unit, wherein the coding unit is coded with a CCP mode.   
     
     
         5 . The method of  claim 4 , wherein a target history table to be updated of the at least one history table is based on a coding mode of the coding unit,
 wherein the coding mode of the coding unit comprises at least one of:
 a cross-component linear model (CCLM), 
 a CCLM based on top neighboring samples of the coding unit (CCLM-T), 
 a CCLM based on left neighboring samples of the coding unit (CCLM-L), 
 a multi-model based CCLM (MM-CCLM), 
 a multi-model based CCLM-T (MM-CCCM-T), 
 multi-model based CCLM-L (MM-CCCM-L), 
 a gradient linear model (GLM), or 
 a CCLM with slope adjustment, and 
   wherein a set of CCP models and related information for classifying samples into a plurality of groups of CCP models are stored in a first history table of the at least one history table, the first history table being associated with CCLM.   
     
     
         6 . The method of  claim 4 , wherein a target history table to be updated of the at least one history table is based on a coding mode of the coding unit,
 wherein the coding mode of the coding unit comprises at least one of:
 a convolutional cross-component model (CCCM), 
 a CCCM based on top neighboring samples of the current video block (CCCM-T), 
 a CCCM based on left neighboring samples of the current video block (CCCM-L), 
 a multi-model based CCCM (MM-CCCM), 
 a multi-model based CCCM-T (MM-CCCM-T), or 
 a multi-model based CCCM-L (MM-CCCM-L), and 
   wherein a set of CCP models and related information for classifying samples into a plurality of groups of CCP models are stored in a second history table of the at least one history table, the second history table being associated with CCCM.   
     
     
         7 . The method of  claim 4 , wherein the coding unit is coded with a cross-component linear model (CCLM) with slope adjustment, and a corresponding CCP model is adjusted by the slope adjustment before being used to update the at least one history table. 
     
     
         8 . The method of  claim 4 , wherein the at least one history table is updated by: adding a set of information related to the at least one model used by the coding unit into the at least one history table,
 wherein the set of information comprises at least one of: the at least one CCP model, the number of the at least one CCP model, a threshold for classifying samples into a plurality of groups of CCP models, or slope adjustment information,   wherein an approach for adding the set of information related to the at least one CCP model into the history table is based on whether the history table is full,   wherein if the history table is not full, the set of information is added to a first vacant entry of the history table,   wherein the first vacant entry comprises one of: a vacant entry with a smallest index in the history table, or a vacant entry with a largest index in the history table, and/or   wherein the first vacant entry with the set of information is put as a last occupied entry in the history table, wherein the last occupied entry comprises one of: an occupied entry with a largest index in the history table, or an occupied entry with a smallest index in the history table.   
     
     
         9 . The method of  claim 8 , wherein if the history table is full, an entry in the history table is removed, and the history table is updated by adding the set of information to a further vacant entry of the history table,
 wherein the entry is with a smallest index in the history table, wherein the updated history table is determined by HT′[i]=HT[i+1], for(<=i<=N−2, where HT denotes the history table, HT′ denotes the updated history table, HT′[N−1] stores the set of information, and N denotes a size of the HT, or   wherein the entry is with a largest index in the history table, wherein the updated history table is determined by HT′[i]=HT[i−1], for 1<=i<=N−1, where HT denotes the history table, HT′ denotes the updated history table, HT′[0] stores the set of information, and N denotes a size of the HT, or   wherein updating of the history table is based on a first in first out approach.   
     
     
         10 . The method of  claim 8 , wherein at least one of whether to update the history table based on the set of information or how to update the history table is determined based on at least one similarity between the set of information and at least one entry in the history table,
 wherein if a similarity between the set of information and a target entry is less than or equal to a threshold, the set of information is not added into the history table,   wherein the target entry is moved to a beginning position of the history table, and an entry in the history table before the target entry is moved one position backward, wherein the history table is updated by: HT′[0]=HT[k]: HT′[i]=HT[i−1] for 1<=i<=k: HT′[i]=HT[i] for i>k, where HT denotes the history table, HT′ denotes the updated history table, HT[i] with i=0, 1 . . . denotes an entry in the history table, HT[k] denotes the target entry, or   wherein the target entry is moved to an end position of the history table, and an entry in the history table before the target entry is moved one position forward, wherein the history table is updated by HT′[N−1]=HT[k]; HT′[i]=HT[i+1] for k<=i<=N−2: HT′[i]=HT[i] for i<k, where HT denotes the history table, HT′ denotes the updated history table, HT[i] with i=0, 1 . . . denotes an entry in the history table, HT[k] denotes the target entry, and N denotes a size of the history table.   
     
     
         11 . The method of  claim 8 , wherein at least one of whether to update the history table based on the set of information or how to update the history table is determined based on coding information of the coding unit with the set of information,
 wherein the set of information is of the coding unit coded with history-based CCP (H-CCP) mode, the set of information is not added into the history table,   wherein a target entry in the history table is used by the coding unit, the target entry is moved to a beginning position of the history table, and an entry in the history table before the target entry is moved one position backward, wherein the history table is updated by: HT′[0]=HT[k]: HT′[i]=HT[i−1] for 1<=i<=k; HT′[i]=HT[i] for i>k, where HT denotes the history table, HT′ denotes the updated history table, HT[i] with i=0, 1 . . . denotes an entry in the history table, HT[k] denotes the target entry, or   wherein a target entry in the history table is used by the coding unit, the target entry is moved to an end position of the history table, and an entry in the history table before the target entry is moved one position forward, wherein the history table is updated by HT′[N−1]=HT[k]: HT′[i]=HT[i+1] for k<=i<=N−2: HT′[i]=HT[i] for i<k, where HT denotes the history table, HT′ denotes the updated history table, HT[i] with i=0, 1 . . . denotes an entry in the history table, HT[k] denotes the target entry, and N denotes a size of the history table.   
     
     
         12 . The method of  claim 1 , wherein a maximum size of a history table of the at least one history table is predetermined, wherein the maximum size is 5 or 6, or
 wherein a syntax element (SE) in the bitstream indicates a maximum size of a history table of the at least one history table, wherein the syntax element is at one of: a block level, a sequence level, a group of pictures level, a picture level, a slice level, or a tile group level, wherein the syntax element is in at least one of the following coding structures: a coding tree unit (CTU), a coding unit (CU), a transform unit (TU), a prediction unit (PU), a coding tree block (CTB), a coding block (CB), a transform block (TB), a prediction block (PB), a sequence header, a picture header, a sequence parameter set (SPS), a Video Parameter Set (VPS), a decoded parameter set (DPS), Decoding Capability Information (DCI), a Picture Parameter Set (PPS), an Adaptation Parameter Set (APS), a slice header or a tile group header.   
     
     
         13 . The method of  claim 1 , wherein a maximum size of a history table of the at least one history table is determined based on coding information,
 wherein the coding information comprises at least one of: a mode of the current video block, a mode of a neighbouring block of the current video block, a mode of a luma block in a collocated region of the current video block, a mode of a luma block in the collocated region of a neighbouring block of the current video block, a quantization parameter (QP), a slice type, a picture type, a width or a height of a picture, a width or a height of a block, or reconstructed samples of the current video block.   
     
     
         14 . The method of  claim 1 , wherein an entry of the at least one history table includes CCP models for a plurality of chroma components,
 wherein the plurality of chroma components comprises a first chroma component and a second chroma component,   wherein the entry is selected for the current video block, and the first and second chroma components of the current video block is coded by corresponding CCP models in the entry.   
     
     
         15 . The method of  claim 1 , wherein an entry of the at least one history table includes a CCP model for a single color component,
 wherein the single color component comprises a first chroma component or a second chroma component, and/or   wherein the entry is selected for the current video block, and a corresponding color component of the current video block is coded by the CCP model in the entry.   
     
     
         16 . The method of  claim 1 , wherein a plurality of history tables of CCP models are determined for a plurality of color components. 
     
     
         17 . The method of  claim 1 , wherein the conversion includes encoding the current video block into the bitstream, or
 wherein the conversion includes decoding the current video block from the bitstream.   
     
     
         18 . An apparatus for video processing comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
 determine, for a conversion between a current video block of a video and a bitstream of the video, at least one cross component prediction (CCP) model for the current video block based on at least one history table (HT) of CCP models; and   perform the conversion based on the at least one CCP model,   wherein the at least one history table of CCP models is updated before or after coding a video unit.   
     
     
         19 . A non-transitory computer-readable storage medium storing instructions that cause a processor to perform a method comprising:
 determining, for a conversion between a current video block of a video and a bitstream of the video, at least one cross component prediction (CCP) model for the current video block based on at least one history table (HT) of CCP models; and   performing the conversion based on the at least one CCP model,   wherein the at least one history table of CCP models is updated before or after coding a video unit.   
     
     
         20 . A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by an apparatus for video processing, wherein the method comprises:
 determining at least one cross component prediction (CCP) model for a current video block of the video based on at least one history table (HT) of CCP models; and   generating the bitstream based on the at least one CCP model,   wherein the at least one history table of CCP models is updated before or after coding a video unit.